The present invention relates to a phenylhydrazone derivative of oxamide useful as active ingredient of herbicidal composition and to the herbicidal compositions containing said derivatives as active ingredient.
Hitherto, 1-(2-tolyl)hydrazone of N-benzoyloxamide and 1-(3-tolyl)hydrazone of N-benzoyloxamide have been reported as phenylhydrazone derivatives of oxamide (Journal of the Chemical Society, 575, 1962). However, no disclosure has ever been made about the phenylhydrazone derivatives of oxamide represented by the following formula (I): ##STR2## (wherein R.sup.1 is straight-chain alkyl group having 2 to 10 carbon atoms, branched alkyl group or cyclic alkyl group having 3 to 10 carbon atoms, alkyl group having 1 to 3 carbon atoms which is substituted with an alicyclic structure having 3 to 7 carbon atoms, phenyl group, halogen-substituted phenyl group, aralkyl group having 7 to 9 carbon atoms, alkenyl group having 3 to 6 carbon atoms alkyl group having 2 to 4 carbon atoms which is subsutituted with alkoxy group having 1 to 4 carbon atoms, or alkyl group having 2 to 10 carbon atoms which is substituted with 1 to 19 fluorine atoms; and R.sup.2 is hydrogen, fluorine, chlorine, methyl group or methoxy group, and the fact that such derivatives have an excellent selective herbicidal activity.
Rice, wheat and corn are the important crops, and use of a herbicide is essential for increasing the yield of such crops by protecting them against harm by weeds. Thus, the development of the herbicides, especially the ones having a selective herbicidal activity enabling killing of weeds alone without doing any practical harm to the crops even if applied to the crops and weeds at the same time, has been strongly desired.
The present inventors have made extensive studies on the compounds showing an excellent herbicidal effect but not doing any practical harm to the useful crops such as rice, wheat and corn, and found that the phenylhydrazone derivatives of oxamide represented by the following formula (I) have the excellent selective herbicidal activities: ##STR3## wherein R.sup.1 is straight-chain alkyl group having 2 to 10 carbon atoms, branched alkyl group or cyclic alkyl group having 3 to 10 carbon atoms, alkyl group having 1 to 3 carbon atoms which is substituted with an alicyclic structure having 3 to 7 carbon atoms, phenyl group, halogen-substituted phenyl group aralkyl group having 7 to 9 carbon atoms, alkenyl group having 3 to 6 carbon atoms, alkyl group having 2 to 4 carbon atoms which is substituted with alkoxy group having 1 to 4 carbon atoms, or alkyl group having 2 to 10 carbon atoms which is substituted with 1 to 19 fluorine atoms; and R.sup.2 is hydrogen, fluorine, chlorine, methyl group or methoxy group.
The present invention was attained on the basis of this finding.
Thus, the present invention has for its object to provide a phenylhydrazone derivative of oxamide having a selective herbicidal activity, that is, showing excellent herbicidal activities against the gramineous weeds and, in particular, broadleaf weeds, while doing no harm to the crops such as rice, wheat and corn, and a herbicidal composition containing such derivatives as active ingredient.